Washington, DC, USA, 5 August 2015 | AAP/AP

Update 3.25pm: Lleyton Hewitt has kicked off his final American hardcourt campaign with a first-round victory over a fellow Australian at the Citi Open in Washington DC.

The 34-year-old Hewitt, who will retire after next year’s Australian Open, had little trouble in accounting for John-Patrick Smith 6-3 6-4 on Tuesday in the US capital.

Of the other Aussies, Sam Groth won through to the second round with a three-set upset over Brazilian Thomaz Bellucci 7-6(8) 4-6 6-3 while James Duckworth went down to Kei Nishikori in a thrilling second round encounter.

> READ MORE: Groth grinds out Washington win

> READ MORE: Gallant Duckworth pushes Nishikori to the brink

Hewitt, who is playing in Washington as a wildcard entry as his ranking has slid to world No.283, is building towards his last appearance at the US Open which starts at the end of the month.

His triumph over world No.133 Smith was only his third win in singles this season in 10 matches.

Wearing his trademark backward white baseball cap, Hewitt pumped his fist.

His six-year-old son Cruz, wearing a backward black hat, rose from his front-row seat in the stands and applauded.

“This is special, having my son here this week,” Hewitt said. “He came to this tournament with me last year. He wanted to do it again. He asked if we’re going back to Washington. I said, ‘We’ll have to see if they give us a wild card.”‘

Tuesday’s victory over Smith was mainly due to him converting three of six break points on Smith’s serve, while saving nine out of 10 that he faced.

“True competitor,” Smith said. “You can’t teach that. It’s something you’re born with.”

Hewitt’s 30 career titles include the US Open in 2001, and Wimbledon in 2002. He won the Washington tournament in 2004, and his name appears in white, capital letters alongside those of other past champions on a blue overhang in the main stadium, where the occasional cry of “Come on, Lleyton!” rang out Tuesday.

“Going back to places like Wimbledon and playing in those places for the last time, you try and enjoy the memories,” Hewitt said, adding Cruz was enjoying his time in the locker room with the other Australian players.

Hewitt next faces Spaniard Feliciano Lopez, who had a first-round bye as the tournament’s No.7 seed.